Very strange speedometer issue

[aknott1994]

My speedometer is having some issues I have never seen before. When I got the truck the speedometer didn't work so I replaced the sensor on the T case and it would bounce a little and that is it. I pulled the gear and it was worn pretty bad in the center so I replace it with one I had on hand(admittedly probably the wrong tooth count) and it works somewhat. It bounces up to 35 then smoothes out but it is progressively more off the faster I go. I thought putting the correct gear on would fix the problem but I am not sure with the issue. Up to 35 it is 5mph off, from 35-50 it is 10mph off, and when it reads 55 I am going 70mph. Why is it varying so much?

 

[tinman_72]

When you put a gear on with the wrong number of teeth, it will be off by a percentage. The faster you go, the more it will be off.
A bouncing speedo is an indication of a worn speedo cable. If you get a new cable (I don't know if they are even available) and the correct gear you should be good to go.

 

[adsm08]

What tinman said.

A bouncing speedo needle, even in only a certain speed range, is usually indicative of a binding cable. However if the cable's gear was worn there is a good chance the drive gear in the transfer case is also worn/damaged.

Years ago my speedo cable got loose from its retainer and laid up against the exhaust. When the plastic casing melted it locked the cable up and that stripped both of the plastic gears.

The gear in the transfer case is pretty easy to inspect. The rear output flanged needs to be removed and then the gear can just be slid out.

 

[RonD]

+1 ^^^

1994 and earlier Rangers used a speedometer cable, the VSS sensor was for the computer and cruise control

So if you have a 1983 to 1994 Ranger then you need a new speedometer cable, and I think it was a bit longer for 4x4's

 

[aknott1994]

So a new speedo cable and the correct gear are in the near future for my truck. Thank you all

 

[bobbywalter]

I usually use the cable from the e series. Usually get a good gear too if it is a 410